This invention relates to radiation curable coatings which cure to provide a pressure sensitive adhesive surface.
Pressure sensitive adhesive (P.S.A.) coatings from aqueous or solvent systems are themselves well known and in common use. The conventional pressure sensitive adhesive systems are made up of rubbery type polymers (elastomeric) and tackifiers (hard resins) which contain extenders, plasticizers and other modifying materials, as needed, in either an aqueous or solvent based medium. These conventional P.S.A. are formulated in a range of 25% to 55% (approximate) total solids in aqueous or solvent media, resulting in the consumption of large quantities of energy for curing and the related problems of solvent removal.
This invention relates to energy curable pressure sensitive adhesives based on a liquid modified urethane oligomer and a non-reactive resinous tackifier, whereby, when cured in-situ under an energy source (UV or EB) it will produce a final product (P.S.A.) comparable to conventional solvent or water base systems, meeting the technical definition of a P.S.A. as given by the "Pressure Sensitive Tape Council". The term pressure sensitive adhesive is used to designate a distinct category of adhesive tapes and adhesives which in dry (solvent free) form are agressively and permanently tacky at room temperature and firmly adhere to a variety of dissimilar surfaces upon mere contact without the need of more than finger or hand pressure. They require no activation by water, solvent or heat in order to exert a strong adhesive holding force toward such materials as paper, cellophane, glass, wood and metals. They have a sufficiently cohesive tackiness, they can be handled with the fingers and removed from smooth surfaces without leaving a residue.